Typically, when we think of solitude, we think of being physically alone.

But I recently came upon another definition of solitude that stopped me in my tracks:

Raymond Kethledge and Michael Erwin define solitude as “a subjective state of mind, in which the mind, isolated from input from other minds, works through a problem on its own.” (xvii)

Let’s really think about that:

Solitude occurs when your mind is isolated from other minds.

That means that you can have mental solitude, even when you’re in a room with other people. Or you can be totally alone — but because you are checking Twitter or responding to email or reading a book — you are still being influenced by others’ words and thoughts.

Kethledge and Erwin suggest that definition in their powerful bookLead Yourself First: Inspiring Leadership through Solitude. (And even if you don’t think of yourself as a “leader” in a formal sense, their definition of leadership includes “leading yourself” — as in, following your own true values and judgement rather than convention or bureaucracy or what others want or expect).

Of course, they aren’t arguing that input from other minds is useless — on the contrary, it is essential to any decision-making process.

But they are arguing that there comes a point when we have enough input.

Great leaders — and the book is mostly a case study in great leaders, from Jane Goodall to Dwight Eisenhower to T.E. Lawrence — are people who seek out moments of isolation from other minds. Through the clarity, insight, and creativity those moments allow for, these leaders are able to make important decisions, discoveries, and creations.

Which leads me to the question: How often in your day are you truly “isolated from the input of other minds” for an extended period of time? What kind of thinking and decision-making is possible, in those moments?